WASHINGTON - The latest US intelligence suggests that the crash of a Russian passenger plane in Egypt was most likely caused by a bomb planted by the terror group Islamic State (IS) or its affiliate, US cable news network CNN reported Wednesday.

A woman holds a candle she attends a meeting to commemorate victims of a Russian airliner which crashed in Egypt, with flight number 7K9268 made of candles seen on the backgroung, outside the Christ the Saviour Cathedral in Moscow, Russia, November 1, 2015.  [Photo/Agencies]

A US official quoted by CNN said: "There is a definite feeling it was an explosive device planted in luggage or somewhere on the plane."

The assessment was reached by looking back at intelligence reports that had been gathered before and after Saturday's crash of the Metrojet Flight 9268 in Egypt's Sinai that killed all 224 people onboard, CNN quoted the official as saying.

But the official added that there has not been a formal conclusion reached by the US intelligence community on the cause of the crash.

The plane, which was heading to St. Petersburg, Russia, crashed about 23 minutes after taking off from the Egyptian resort city of Sharm el-Sheikh. Most of the passengers were Russian citizens.

There "had been additional activity in Sinai that had caught our attention," the US official said.